Clarification



Sept. 18, 1951 E. M. KELLY ET AL CLARIFICATION Filed May 51, 1949 qmK ERR mm E wwwkwh \l! mm H MEX INVENTORS. 54% M 16:10;

h |1- lllwi @WIW 1 QN RN Patented Sept. 18, 1951 UNITED STATES PATEN 2,568,452

QLARIFICATIQN Earl M. Kelly, *Millbrae, and Arthur M. Kivari,

Los Angeles, Calif assignors to Process inec s inca cera ed n F an s o, .Qa t,

corporation of California ApplieationMay3-1, 1949, Serial No.9(i,"184' I 1.1.2 filaims 1 This invention is concerned with clarification and provides improvements in methods and rap: paratus for clarification, i. e. the settlement of finely divided solids from suspensions in liquid.

Clarification ordinarily is conducted by intro.- ducing the suspension to be clarified into a tank in which the solids are settled out, the clarified liquid being removed at an overflow and the settled solids being raked to and removed from a central discharge point at the bottom of the tank. Such apparatus is satisfactory in many instances, but his always advantageous toobtain as large a throughputas possible. 'In many instances, settlement is influenced by flocculation or agglomeration of the finely divided solids in the original suspension, thus increasing settlement and it has been suggested that the settling rate and the Yclarifiertcapaci-ty can both be in creased by returning some of the settled sludge into the upper portion of the clarifiertank to provide nuclei to which more finely divided solids may be attached, ior example, iby agglomeration or adsorption.

As .a result of our investigations "we have discovered that the rate of settlement or clarification can :be increased *by circulating both settled and partially settled solids in the clarifler tank in contact with incoming :feed and with air. his discovery is applicableto the clarification of weter supplies, sewage treatment. and to the :olarincation of liquids containing chemical precipitates, such ior example, as those 1 oduced in the lime-soda process of water softening. Accordingly, .our invention contemplates, in a clarification operation involving settlement of finely divided solids suspended in a liquid body, the improvement wh ch comprises continuously lift- .ing settled solidsmixed-with air ircrn alower portion of the #130 15 adjacent to the point :of smoval of the settled solids and theqdischarge of thi m u e 1111117 he upp porti o t e od continuously lifting partially settled solids from .an intermediate level :the .ibody to sa upper :pontion'of the bodyand continuously in roduc n fresh Freed "into the .upper portion iof the body. In this fashion, the fresh feed is circulated in contact with both partially suspended settled .solids and completely settled solids, th effect being to increase the rate of clarification her petatlement.

The reasons for the improved results are :not omp y understood, but it is believed that th partially settled solids provide more tiav ra le nuclei .ior agglomeration or adsorption {of .tso ne .z a t or l ss eom le e y ettles lids erotics more w arabl nu lei for the sonselida ion of. eth r solids nth ed i It i desirable t e tablish body see currcntc rcu ation ofth s. thessratai ttled solidsandthe aerated par Pref rably h .fr sh ice introduce .199 the same unner unis its? an. O whi the circulated sett e .2 and the eas-ta ly s ttles s li are intro uced.- y l y. t

n slande comes; as tees tor reta ing a P 1 liquid is Whig s a ifies ie l t e see an upper peripheral dis .,-s s m nsf qi c n fl l q d t a n the tan s cl ts: d abetes was? e t ed s i s an ea s v q im v I settled solids to the lower dischargen eaps a orig the bottom of the tank, our invention contein'pl'at'es the combination which comprises means foi con tinuously introducing a suspension "offin'ely di vided solid's'in liquid "tobe clarified into an upper portion of the tank. an airlift for lifting settled solids from a point adjacent the'lower discharge means to a point in the upper portion of the tank and there disehargingthe settled solids into the pool, and means for blowing air into the tank at an intermediate level or raising partially settled solids "into the upper portion of the tank into which the settled solids are discharged by the airlift. Preferably the apparatus of the in.- vention is provided with means for adjusting the ratio of settled and partiatly settled solids that are liftedand recirculated/becausewe have-iound that 'for many cases thereisan optimum ratio which, when attained, gives cptimumclarification conditions. i

In th pr fe ed :fqnn of th pp ratus of th invention a c n e co umn is p ov ded. h ma.- teria to be marines e ree-s o in o this co um A s utalit of duct-stride eirlitts :fo s t l d sludge a e dis se vertical a un th s center column. -w. 111 a separate control :for' the rate o li t-or circ lation o e ch duct 1 .1 addi tion, the apparatus i .providedwith an air rin which introduces air around the center column at anintermcd ateileve zinithe se i lhis air causes part ally settled .asol ds to be aerated a diliited toward the surface .andrcirculated sinicontact with the. returned settl d slud e and the trash teed. Preferably lmeans .z bould be provided sfor con.- trolling the amount of. air admitted .at :the inter;- mediate level, thus controlling ithe rate .of areuturn.- or recirculation of the partially settled solids. v i

fllheseandother aspects o the intention wil pf theimaterialiin oneiresh afeed. whileithe more .55 lhfiHQdSfl-fiIQQd mor clear yi -theilisht fathesoh 3 lowingdetailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a sectional elevation of a clarifler incorporating the elements of the invention and adapted for sewage treatment; and

Fig. 2 is a partial plan view of the apparatus of Fig. 1.

" The apparatus illustrated comprises a conventional round tank In of concrete or the like, having a gently sloping inverted conical bottom ll and a vertical wall I IA. A conventional annular overflow'launder I 2 is provided at the top periphery of the tank to receive clarified liquid. A vertical annular baffle l3 of stlplate or the like is disposed vrtically in the tank about a third of the way in from the wall and is held in position by a steelskeleton framework 14 which is fastened to the inside of the wall of the tank.

The apparatus has a central column or hollow shaft l5 7 which rises vertically and supports a turntable H5 at its top. A drive truss I I rests and rotates 'onthe turntable and extends to a track l {A on the inside wall of the overflow launder. The drive truss rests on drive wheels I9 which in turn rest onthe' track. The wheels are driven in conventional fashion by a motor l8 mounted on the underside of the drive truss. A skeleton framework is rigidly fastened to the drive truss and extends downwardly around the central shaft of the apparatus. It carries a 7 from the pocket through a pipe 24.

t A conventional scum scrapper is fastened to the drive truss between the overflow launder and the'annular baflle. scum from the surface of the liquid in the outer tank annulus and discharges it into a scum box '26 of conventional type disposed between the-annular baffle. and. the outside of .the tank. The scum box is drained through a pipe 21 into an outside launder or tank 28. Fresh sewage to be treated is introduced into thebottom of the apparatus and rises through the hollow center shaft where it escapes just below the liquid level 29into the pool 30. The fresh sewage passes out of the central shaft through four equal ports atthe same elevation. Two of the ports 3|, 32 are shown in Fig. 1. Air under pressure is introduced through a vertical airline .38 which rests on the raking mechanism. This air ring has perforations 39 around its upper surface. e

t The apparatus is provided with four vertical airlifts, of which two 4|, 42 are shown in Fig. 1.

.The airlifts are stationary vertical pipes that extend from a level just above the sludge pit to a level justbelow the discharge of fresh sewage into the pool and are fastened to the outside of the central column. Air for the lifts is supplied by four separatepipes (of which two 43, 44 appear in Fig. 1) which extend from the central air pipe 33 down to a levelabout midway of the airlifts. Each-ofthe lines to the airlifts is provided with The scum scrapper carries 7 separate valves (41, 48 on 'Fig. 1) for control of air to the individual lifts.

The operation of the apparatus just described 7 is as follows:

"and circulate with the fresh sewage. In addi tion, partially settled solids are forced upward from' an intermediate level in the pool by the air emitted by the air ring, so that in the upper cen-' tral zone of the pool there is an admixture of freshly introduced sewage, settled sludge that has been aerated and returned, and partially settled sludge that has been aerated and returned. The effect of the airlifts and the air ringis to set up a circulation in a radial plane from top to bot: tom of the clarifier .(see the arrows 60 in Fig. 1). Liquid (see the arrowGl in Fig. 1) passes underneath the annular bafiie I3 which drops down so that it just clears the rake mechanism and thence passes upward in the outer annular section 10. Scum rising in this outer annular section is dragged off by the scum scraper into the scum box. Clarified liquid rising in the outer annular sec+ tion passes through a plurality of ports H into the peripheral launder of the clarifier and'thence is discharged. I

It should be emphasized that the central shaft or column of the clarifier is stationary and that the air lifts disposed. on the outside thereof are likewise stationary.

The structure illustrated in Figs. 1 and I2 is adapted for tanks of 40 feet or more in diameter. For smallertanks it is preferable to support the rake structure, and the aerating means from beams extending crosswise of the tank in conventional manner.

a The feed preferably is introduced below the liq' uid level in the central portion or the pcolas shown in Fig. 1, but it may be introduced at any point in the pool within the bafile. Thus the feed maybe introducedby a pipe passing through the side of the tank and the baffle or coming into the tank from above. 7 By controlling the air sent to the perforated air ring and to the airlift, the rate of circulation of the settled sludge and the partially settled Sludge can be adjusted with respect to eachother and with respect to the rate of introduction of fresh sewage. i j .7 Conditions for coagulation and settling are par.- ticularly advantageous in the apparatus of the -ve'ntion due to the fact thatsettled sludge, pariti'ally settled slude and raw feed rise at the center of the clarifier and are aerated near the liquid surface, 1. e. near the surface of. the pool. Morever, coagulation is aided by exposure ofthe risins stream to the air at the pool surface. .j I l l As indicated above, the invention hasbeen dean m a scribed in detail with referenceto sewagestreat ififltflbliflbdtli the process'and apparatus are applicable tb' a'great variety of cl'arificatidmprbb lems including the removal of chemical'precipitates from "mother liqiiorsfetc.

1. In clarification involving the flocculation and settlement of finelydivi'ded solids suspended l n b dy of liquid it ntinuous remova of the clarified liquid from an upperportionof the body, removal of suspended ,solids from a lower portion of the body, and continuous introduction of feedto the body, the improvement which "corriprises-continuously and separately lifting setu d 'ds with air from" the lower pbrtiofnfof bodyadjacent the po'int'of finoval and' *Eharg'i ng the mixture into an upper portion pr itlie bo'dyf"ontinuously lifting "partially settled it ds vtithair from an intermediate lvel ifi the to said upper portionof' the body, a'nd'cb'nti'iidofisly "discharging fresh feed' into afidpper points of the body remote from the regiomfrdm Which" the "clarified liquid is withdrawn? WY Iri' clarification involving "the flocculation and settlement of finely divided solids suspended ifi' 'a bod'ypf liquid with continu'cius reiiio'v'al of the clarified liquid from an upper portion of the body, removal of suspended solids from a lower portion of the body, and continuous introduction of feed to the body, the improvement which comprises continuously and separately lifting settled solids mixed with air from the lower portion of the "body adjacent the point of removal and discharging the mixture into an upper portion of the body, continuously lifting partially settled solids with air from an intermediate level in the body to said upper portion of the body, continuously discharging fresh feed into an upper portion of the body in the neighborhood in which the mixture is discharged, and establishing in the body a concurrent circulation of the feed, the aerated settled solids and the aerated partially settled solids.

3. In clarification involving the flocculation and settlement of finely divided solids suspended in a body of liquid with continuous removal of the clarified liquid from an upper portion of the body, removal of suspended solids from a lower portion of the body, and continuous introduction of feed to the body, the improvement which comprises 0 continuously and separately lifting settled solids mixed with air from the lower portion of the body adjacent the point of removal and discharging the mixture into a central upper portion of the body, continuously lifting partially settled solids with air from an intermediate level in the body to said central upper portion of the body, and continuously discharging fresh feed into said central upper portion of the body in the neighborhood in which the mixture is discharged.

4. In a clarifier comprising a tank having an upper peripheral discharge means for clarified liquid, a lower discharge means for settled solids, and means for moving settled solids to the lower discharge means along the bottom of the tank,

the combination which comprises feed means for continuously introducing a suspension of finely divided solids in liquid to be clarified into an upper portion of the tank remote from the peripheral discharge means for clarified liquid, an airlift separate from the feed means for raising settled solids from a point adjacent the lower discharge means to a point in said upper portion of the tank closely adjacent the paint of discharge from said feed means and there discharging it,

and separate meaiis for blowln'g air into the "atfan ifitefmediaw lvel for' raisifig'partiallyfsetltleii" studs intd said ,u per edition or the tank into which the "settledfsolids Y are discharged b? the airlift.

5. In aclarifier comprising a tank=having an upper peripheral d'isoharge'ineans for clarified liquid, a slower discharge" means 'rcr; ett1eu solids, means for moving settled solids "to wan er discharge means along the bottom of the"; nk, "thc conibina'tion which comprises feed means fr ciintini ously introducing a suspension df fi y dividewsolids in Iiduid't'o' be 'clari-fi'ed into an uppefportion of the tank remote fromthe ief- IfiQIieraLiiiScHarg'e"means, an: airlift separate rrorn the feedrrieans fo'r raising settled stats from a "point adjacent the 1ow r discharge peas totem-upper portion'of the tankclosely adia} centthe point bf discharge from said feed in ns "and theredis'chargingit, "and separate inc n3 for blowing "air-"1Q to" the-tank below said upp r portion at an intermediate lvel for raising riaiitially' settled solids mtdsaid' upper "'po t me; ytfiJ- l l y l" a n. M n wi- B."'Ih a clarifier comprising a tank having an upper" peripheral discharge" meets" for" clarified liquid, a central lower discharge means for settled solids, and means for moving settled solids to the central lower discharge means along the bottom of the tank, the combination which comprises feed means for continuously introducing a suspension of finely divided solids in liquid to be clarified into an upper inner portion of the tank, at least one airlift separate from the feed means and disposed upright adjacent the center of the tank for raising settled solids from a point adjacent the lower discharge means to a central upper portion of the tank closely adjacent the point of introduction of the feed and there discharging it, and a aeration means disposed around the airlift for blowing air into the tank at an intermediate level for raising partially settled solids into the central upper portion of the tank.

7. Apparatus according to claim 6 in which the airlift is stationary and means are provided for rotating the aeration means around it.

8. Apparatus according to claim 6 in which the airlift is provided with a separate control valve for the amount of air introduced into it.

9, Apparatus according to claim 6 having a separate valve for controlling the amount of air admitted to the aeration means.

10. Apparatus according to claim 6 in which a valve is provided for separately controlling the amount of air admitted to the airlift, and another valve is provided for separately controlling the amount of air admitted to the aeration means.

11. In a clarifier comprising a tank adapted to contain a pool of liquid from which finely divided solids are settled, an upper peripheral discharge means for the clarified liquid, a lower central discharge means for the settled solids, and means for moving the settled solids along the tank bottom to the central discharge means, the combination which comprises an airlift for raising settled solids admixed with air and liquid from a point adjacent the central discharge means and projecting the mixture toward the tank side into an upper central zone in the pool, means for blowing air into the pool at a point intermediate the central discharge means and the upper central zone to cause partially settled V of air introduced into the airlift and through the air blowing means. v

12. In a clarifier comprising a tank adapted to contain a pool of liquid having its upper surface in contact with the atmosphere and from which finely divided solids are settled, an upper peripheral discharge means for the clarified liquid, a lower central discharge means. for the settled solids, and means 'for movingthe settled solids along the tank bottom to the central discharge means, the combination which comprises at least one airlift for raising settled solids admixed with air and liquid from a point adjacent the central discharge means and introducing the mixture into an upper central zone in the pool near the surface, means separate from the ried up into the zone, and means for adjusting the ratio of the air introduced through the air lift and the air introduced through the air blow.-.

ing means.

EARL M. KELLY. ARTHUR M..KIVARI.

REFERENCES CITED 'The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 830,552 Zeigler Sept. 11, 1906 2,078,266 Morehead Apr. 27, 1937 2,126,288' Streander Aug. 9, 1938 2,144,385 'Nordell Jan. 17, 1939 2,223,257 Mallory 1 Iov. 26, 1940 2,370,356 Kamp et al 'Feb.' 27,1945 2,370,974 Langdon Mar. 6, 1945 2,400,598 Prager May 21, 1946 2,404,223 Durdin July 16, 1946 2,411,390 Prager Nov. 19, 1946 2,477,459 Kelly; July 26, 1949 2,492,486 Kivari et a1 Dec. 27, 1949 2,506,927 Kelly May 9, 1950 

1. IN CLARIFICATION INVOLVING THE FLOCCULATION AND SETTLEMENT OF FINELY DIVIDED SOLIDS SUSPENDED IN A BODY OF LIQUID WITH CONTINUOUS REMOVAL OF THE CLARIFIED LIQUID FROM AN UPPER PORTION OF THE BODY, REMOVAL OF SUSPENDED SOLIDS FROM A LOWER PORTION OF THE BODY, AND CONTINUOUS INTRODUCTION OF FEED TO THE BODY, THE IMPROVEMENT WHICH COMPRISES CONTINUOUSLY AND SEPARATELY LIFTING SETTLED SOLIDS MIXED WITH AIR FROM THE LOWER PORTION OF THE BODY ADJACENT THE POINT OF REMOVAL AND DISCHARGING THE MIXTURE INTO AN UPPER PORTION OF THE BODY, CONTINUOUSLY LIFTING PARTIALLY SETTLED SOLIDS WITH AIR FROM AN INTERMEDIATE LEVEL IN THE BODY TO SAID UPPER PORTION OF THE BODY, AND CONTINUOUSLY DISCHARGING FRESH FEED INTO AN UPPER PORTION OF THE BODY REMOTE FROM THE REGION FROM WHICH THE CLARIFIED LIQUID IS WITHDRAWN. 